1. Field of the Invention
The present invention relates to a vehicle suspension system and, in particular, to a vehicle wheel suspension system having a suspension member extending generally in the longitudinal direction of the vehicle body which controls movement of the wheel in the longitudinal direction of the vehicle body.
2. Description of Prior Art
Various types of vehicle suspension system have been proposed for supporting wheels on the vehicle body, one of which is provided with a suspension member extending in the longitudinal direction of the vehicle body and supporting a wheel on the vehicle body. This type of suspension member includes a trailing arm or a leading arm. For example, in the trailing-arm type suspension, the trailing arm is disposed in front of the wheel and extends in the longitudinal direction of the vehicle body with its front end pivotally connected to the vehicle body and its rear end pivotally connected to a wheel support member, by which a wheel is supported swingably on the vehicle body. As the main means for providing the trailing arm with a resilient supporting characteristic in the longitudinal direction, a rubber bush means is interposed as a resilient means in each of the connecting portions of the trailing arm. If the rubber is soft and produces a large amount of deformation with respect to a longitudinal force applied thereto, the shock due to the application of longitudinal force via the wheel can be largely absorbed by the bush and the riding comfort can be improved. However, in case that the bush is deformed too much, the toe angle of the wheel tends to change excessively, which adversely affects the motive stability and drivability of the vehicle.
Accordingly, the trailing arm system is typically set such that it exhibits a resiliently soft characteristic with respect to a rearward force acting on the wheel caused by the driving resistance while it exhibits a resiliently hard characteristic with respect to a frontward force acting thereon. Japanese Utility model Public Disclosure No. 139040/1981 discloses this type of trailing arm system, in which a trailing arm extending frontward with respect to a vehicle body is connected at ends to the vehicle body and a wheel via specially designed rubber bushes, respectively. These rubber bushes provide the trailing arm system with the above-mentioned resilient characteristics.
Shock absorbing means is also provided in a conventional vehicle suspension system. Recently, a proposal has been made to use a shock absorbing member such as a damper and a spring means wherein such member is arranged so as to incline rearward for the purpose of lowering the bonnet of the vehicle body to obtain a better frontward view through the windshield or of obtaining a larger amount of room in the rear portion of the passenger compartment. In operation, upward forces acting on the wheel from the road surface, which are caused by the uneveness of the surface, are applied to the connecting end of the inclined shock absorbing member from the wheel side. Due to the inclination of the member, the reaction force in response to the upward force acts on the wheel in the inclined direction. This inclined reaction force presses the wheel in both downward and forward directions at the same time. Where the wheel is supported by the trailing arm system having a resiliently hard characteristic with respect to the forward force, the forward component of the reaction force may not be absorbed by the trailing arm system and a shock may be produced by that component. However, no proposal has been made in the prior art for improving the riding comfort of this type of suspension system with an inclined shock absorbing member.